diagram connecting science © hodder education 2009
TRANSCRIPT
• DIAGRAM
Connecting Science © Hodder Education 2009
How a vacuum flask works
• Use the hot spots for the labels on the diagram to find out how the vacuum flask minimises heat loss by conduction, convection and radiation.
• DIAGRAM
Connecting Science © Hodder Education 2009
Vacuum
• The narrow gap between the two silvered walls is evacuated – it contains no air.
• There is no convection in this vacuum space.• No heat can be transferred by conduction in the
vacuum space.
Return to diagram
• DIAGRAM
Connecting Science © Hodder Education 2009
Plastic stopper
• Conduction can only occur at the points where the walls meet the rest of the flask.
• Trapped air between the plastic cup and the stopper acts as an insulator.
• This reduces heat transfer by conduction and convection.
Return to diagram
• DIAGRAM
Connecting Science © Hodder Education 2009
Silvered walls
• The walls around the vacuum flask are made of glass with a silvery coating made of aluminium .
• The shiny surfaces reduce heat loss by radiation (radiated energy is reflected off shiny surfaces).
• The walls could also be made of stainless steel, which can be polished.
Return to diagram